Trimmatostroma leaf spot

Trimmatostroma leaf spot is a fungal disease caused by Trimmatostroma betulinum, which primarily targets various species of birch trees. This pathogen is known for inducing leaf lesions and necrosis, which can significantly affect the health and aesthetic value of birch stands in both forestry and urban landscape settings.

The disease mainly affects birch species such as Betula pendula and Betula pubescens. It can be found in nurseries, parks, and natural forests, especially in regions with cool, humid climates. While it rarely kills adult, healthy trees directly, the stress caused by recurring infections makes them susceptible to other secondary pests and environmental stressors.

The primary symptoms include the development of spots on leaves that range from brown to black, often exhibiting irregular shapes. As the disease progresses, the central parts of the spots become necrotic. Under high humidity, you can observe the formation of fungal structures known as sporodochia, appearing as tiny black specks on the leaf surface, leading to leaf curling and premature senescence.

The development of Trimmatostroma betulinum is heavily dependent on wet weather conditions. Rain splashes play a crucial role in spreading spores from leaf litter or infected twigs to healthy foliage. The pathogen survives the winter in fallen leaves and on the bark of twigs, making the persistence of the fungus a major concern for the next growing season.

To control and prevent the spread of this fungus, integrated management is necessary. Key steps include the removal and destruction of fallen leaves in autumn to reduce the primary inoculum load. During the growing season, if infections are severe, protective fungicides may be applied. Proper tree spacing and canopy management to improve airflow are also essential cultural practices to mitigate the humidity levels that favor the pathogen.